F3K is the international contest class for radio controlled, hand-launched model gliders. Although the roots of RC hand-launched gliders can be traced back to the late 1970s, F3K is a relatively new aeromodelling discipline, becoming officially recognised by the FAI (international body responsible for aeromodelling competition disciplines) in 2007. F3K gliders are limited to a 1.5 metre
wingspan. F3K competitions consist of a group of fliers completing a number of pre-defined flight tasks involving launching, flying and landing the model in a number of timed durations. Just the hand launch and
thermal currents of rising air (thermals) are used to sustain the flight. Since thermals cannot be seen, F3K pilots rely on ground signs such as surface wind velocity, temperature and direction; signs such as circling birds, bugs, or rising particulates; and changes of direction or attitude of the glider due to the thermal itself. The pilot uses these signs to resolve the approximate location of the thermal. For F3K tasks where longer durations are needed, positioning and maintaining the model glider in thermal rising air is paramount. Contest strategy includes determining the location of thermals before the pilot launches. Discus launched gliders can be made from a combination of foam, balsa, carbon fiber, kevlar, and other materials. Prices of these models range from $100 to $900 plus. ==See also==